1. Field of the Invention
The present invention relates to a disposable soft tissue biopsy instrument or more specifically, a cannula and stylet assembly. The disposable biopsy instrument of the present invention provides an oriented, spaced relationship between a hub of an inner sampling stylet and a hub of an outer cannula. The assembly is oriented such that the sharpened distal ends of the cannula and of the sampling stylet are oppositely directed and cannula and stylet hub subassemblies of the needle assembly allow for quick proximal withdraw of the sampling stylet from the cannula for inspection of the sample without removal of the cannula from the biopsy site.
More specifically, the stylet and cannula hub subassemblies are constructed: (a) to provide for smooth forward advance of the stylet hub assembly onto a leg proximally extending from the proximal end of the cannula hub assembly with minimal force forwardly when an actuating device causes relative movement between the subassemblies; and (b) with a distal tip member of a stem portion of the stylet hub assembly and a rail stop at the proximal end of the rail of the leg of the cannula hub assembly which engage each other for positioning the cannula needle and stylet in a desired firing position, and which prevents accidental backout of the stylet hub assembly from the cannula hub assembly and undesirable rotation of the sampling stylet.
2. Description of the Related Art Including Information Disclosed Under 37 CFR .sctn.1.97-1.99
Sampling of inner tissue on humans and animals, a so-called biopsy, has become an increasingly common procedure for the diagnosis of malignancies and for other medical uses. Typically, biopsy instruments include a needle assembly comprising a hollow outer needle (cannula) and an inner needle (sampling stylet) slidably provided therewithin. The sampling stylet has a sharpened distal end and an adjacent biopsy sample-receiving notch which is telescopically disposed within the cannula and extendible from the distal end of the cannula. When so extended, the surrounding tissue expands into the sample-receiving notch of the sampling stylet. Thereafter the cannula is pushed forward to cover the stylet thus cutting-out a tissue sample which is thereby collected in the sample-receiving notch of the sampling stylet and retained by the surrounding outer cannula. When the tissue sample is taken, typically the entire needle assembly containing the collected tissue sample is withdrawn whereupon the sample can be taken out and analyzed.
The Travenol TRU-CUT.RTM. biopsy needle available from Travenol Laboratories, Inc. of Deerfield, Ill. and the subject of U.S. Pat. No. 3,477,423 is an often used biopsy needle comprising a hollow tubular cutting cannula having a sharpened distal end attached to a plastic handle. A coaxial solid stylet telescopes within the cannula and is attached to a knob at its proximal end. The distal end of the stylet is sharpened and includes a traverse slot or specimen notch adjacent to the sharpened end. To obtain a biopsy sample using the Travenol needle, the physician positions the stylet up to or in front of the area to be biopsied, whereupon advancement of the needle assembly is halted. The stylet is then manually advanced distally of the cannula with the cannula held stationary. Upon advancement of the stylet, the specimen notch is exposed. Tissue surrounding the stylet contracts into the specimen notch and the cutting cannula is then manually advanced distally over the stylet, slowly shearing off the tissue entrapped in the stylet's specimen notch. The instrument is then withdrawn and the stylet advanced distally to expose the tissue for preparation for study. If the sampling was not successful, the stylet may be reinserted into the cannula, which remains positioned within the patient, and an attempt to reposition the assembly of the stylet and the cannula and repeat sampling can be made.
Such technique using this basic design of a biopsy instrument is referred to as a manual technique. One drawback to the manual technique is that it requires a great deal of manual dexterity and motor coordination, along with the use of both hands, to advance the stylet while maintaining the position of the cannula and then to maintain the position of the stylet while advancing the cannula.
The Beraha U.S. Pat. No. 4,600,014 discloses a transrectal prostate biopsy device which comprises a handle held in a physician's palm, and a guide tube extending forwardly of the handle. A cannula is slidably disposed within the guide tube and is movable from within the guide tube forwardly out of the distal end of the guide tube. A sampling stylet is telescopically disposed within the cannula and projects from the rear of the handle. A knob is provided at the proximal end of the stylet for extending a distal end of the stylet out of the distal end of the guide tube to expose a sampling thereon. The physician holds the handle in one hand using his index finger at the distal end of the guide tube to guide the instrument to a selected transrectal point on the prostate. Upon locating the point, one hand holds the instrument steady while the other hand pushes the stylet forward and then pushes the cannula over the stylet to sever the tissue within the sampling slot. The device is then withdrawn to gain access to the sample. In one embodiment of the device, the cannula, when in the retracted position, is spring loaded by means of a compressed spring. A release lever, which works against the compressed spring can be activated to release compression of the spring which then expands and pushes the cannula outwardly over the stylet.
A fully automatic instrument is described in U.S. Pat. No. 4,699,154. This instrument comprises a reusable, spring-loaded box-shaped housing or handpiece, which activates a disposable cannula and stylet set. Both the stylet and cannula are activated in rapid succession.
The instrument has the advantage of eliminating the dexterity and motor coordination necessary in use of manual devices and also eliminates the slow cutting action of the manually advanced cannula and replaces it with a very quick, clean cut.
The Goto et al U.S. Pat. No. 4,735,215 teaches a Soft Tissue Biopsy Instrument wherein a stylet extends through a cannula mounted in a distal outer barrel member and is press-fitted into a stylet hub that is press-fitted into a locking ring that is threadably received on a mounting ring fixed in a proximal outer barrel member. The stylet hub is received in an inner proximal barrel member. To remove the stylet the proximal outer barrel member must be unthreaded from the distal outer barrel member and then the locking ring/stylet hub must be unthreaded from the mounting ring.
In the Taylor U.S. Pat. No. 4,881,551 there is disclosed a soft tissue core biopsy instrument wherein a stylet extends through a proximal outer barrel member and distal inner barrel member, a proximal portion of which is received in the proximal outer barrel member and a cannula mounted to a cannula hub received in the distal inner barrel member. A proximal end of the stylet is mounted to a stylet hub which has a bifurcated proximal end portion defined by two fingers. Each finger has a detent thereon which is snap-fittingly received in a recess inside a proximal end of the proximal outer barrel member. The fingers are squeezed together to release the detents from the recess to remove the stylet. The mating recesses and detents serve to locate the stylet longitudinally and rotationally.
The oriented biopsy needle assembly of the present invention maintains the inner stylet hub and the outer cannula hub in a spaced oriented relationship whereby the user thereof may properly load or position the entire needle assembly into a reusable gun introduced without orientating the stylet hub and cannula hub into the gun individually. Alternatively, the orientation of the stylet and cannula hubs can be maintained such that the needle assembly can be positioned into the patient without necessarily, or first, loading the needle assembly into a reusable gun. This advantageously allows a physician to pre-position the needle assembly in a patient and scan the area to be biopsied confirming the correct position of the needle with scanner techniques such as MRI, CAT, and ultrasound independent of the reusable gun which is large and heavy and requires the user to maintain control of the gun handpiece at all times. Thereafter the stylet and cannula can be either advanced manually or with the aid of the automatic gun, such as the Radiplast AB tissue sampling device described in the Lindgren U.S. Pat. No. 4,699,154. The oriented spaced relationship between the cannula hub assembly and the stylet hub assembly conforms to the loading position of the Radiplast tissue sampling device merely by establishing a conforming length between the stylet hub and the cannula hub of the needle assembly of the present invention.
Further, the needle assembly of the present invention orients the assembly such that the sharpened distal ends of the stylet and cannula are oppositely directed and are so maintained free of undesirable rotation hindering successful biopsy collection.
Still further, the stylet is easily proximally removed from within the cannula such that examination of the biopsy sample may be taken without removing the cannula from the biopsy site.
The above attendant advantageous features also promote the desirable goals of minimizing the time required for biopsy and providing a disposable surgical instrument adapted for biopsy procedure utilizing scanning technologies.